Quantum computers could potentially break blockchain security, threatening billions in crypto assets - but how close are we really to this quantum apocalypse?
Quantum computers are all the buzz right now.
Ranging from financial modeling to materials science, drug discovery, climate modeling and more, quantum computers can be applied to myriad use cases that classic computers typically struggle with.
If you’ve been paying attention to the news lately, you’ve probably heard about the ground-breaking capabilities of Google's new state-of-the-art quantum chip, known as Willow.
To put its power into perspective, the 105 qubit processor "performed a computation in under five minutes that would take one of today’s fastest supercomputers 10 septillion years to solve”, per the original announcement.
Rumors are now circulating that quantum computers could begin to pose a threat to the Bitcoin network and other cryptographically secured ledgers. Some of the most optimistic predictions suggest that Bitcoin’s security measures could be toppled within just 3 years.
Is there any substance to these claims? Let’s take a deeper look.
N.B. We’ll primarily focus on the Bitcoin blockchain since it’s the most battle-tested and the inspiration for the vast majority of distributed ledgers.
What Are Quantum Computers?
Unlike classical computers, which use bits (which can be either 0 or 1) as the basic unit of data and perform operations linearly using logical gates; quantum computers use qubits (which can be both 0 and 1 simultaneously) and process operations in parallel thanks to their quantum gates.
This might sound like technical garble, but these differences make quantum computers a radically different technological marvel compared to even the most powerful supercomputers.
Quantum computers are the ideal tool for tackling complex problems that require the exploration of vast combinations and possibilities in areas like cryptography, quantum simulation, optimization and machine learning.
It has been said that it will require the unique capabilities of a quantum computer to solve problems like Schrödinger equations for molecule simulation, accurate climate modeling, efficient drug discovery and more.
Herein lies both the potential and risks associated with quantum computers. While they can be used to crack centuries-old challenges that have plagued us as a species, they might also threaten existing mechanisms that secure our digital infrastructure, necessitating the development of new quantum-resistant cryptographic methods to safeguard sensitive information and communications.
But how much of a threat to Bitcoin are they in their current state? Let’s find out.
Can Quantum Computers Break Bitcoin’s Encryption?
The short answer is… no, but that could change in a few decades.
A sufficiently powerful quantum computer would eventually crack the various security layers that secure Bitcoin's blockchain, such as the SHA-256 hashing and the elliptic curve digital signature algorithm (ECDSA) used for generating Bitcoin wallets and transactions.
They excel at a type of unstructured search problem solving. In essence, this means they are able to search through large sets of data significantly faster than classical computers.
When this processing capability is focused using Grover’s algorithm, it could be used to crack the SHA-256 hash function by finding the input that produces the specific hash that it needs to crack.
>> Click here to read more about SHA-256.This would provide a significant advantage when it comes to mining new blocks. But it wouldn’t outright break the security of the network.
Cracking ECDSA would be a much bigger problem, since the quantum computer could use Shor’s algorithm to derive private keys from public keys — something that is nigh impossible for traditional computers that rely on brute forcing.
If ECDSA were cracked, an attacker could potentially derive private keys from public keys, thereby gaining control of the Bitcoin held at these addresses and forging transactions. That said, some Bitcoin address types (i.e. Bech32 addresses) offer an additional layer of security against quantum attacks.
According to an analysis by Deloitte, approximately 20% of the Bitcoin supply is currently vulnerable to this type of attack.
That said, designing such a system remains well beyond our current capabilities — something that isn’t likely to change for several decades.
According to estimates by scientists from the University of Sussex, a quantum computer would need >1.9 billion qubits to crack SHA-256 within 10 minutes, whereas it would take a whopping 13 million qubits to crack ECDSA 256 within a day. This number increases to 300 million qubits to crack ECDSA 256 within an hour.
That said, one paper suggests just 1536 fully error-corrected qubits (known as logical qubits) could theoretically crack Bitcoin.
Currently, the most advanced fault-tolerant quantum computer wields just 24 logical qubits.
Given the current pace of quantum computer development, it would likely take several decades for systems to reach the capabilities necessary to threaten most modern cryptographic security measures.
Since the risk of errors increases with the number of qubits in a quantum computer, advanced error correction technologies and improvements in qubit coherence would need to be developed. This remains an unsolved engineering and theoretical problem.
If quantum computers ever reach the computational might necessary to crack ECDSA, practically everything that relies on encryption methods and/or elliptic curve cryptography will be at risk. This includes internet and mobile communication networks, encrypted data, VPN networks, biometric identification and more.In other words, if such a quantum computer were to be invented any time soon, its effect on Bitcoin would be the last thing you’d be worrying about.
Can Blockchains Upgrade Their Security?
As it stands, it is indeed technically feasible for some far-flung quantum computer to eventually crack the mechanisms that secure the Bitcoin blockchain.
Fortunately, the Bitcoin network evolves over time by gradually incorporating Bitcoin Improvement Proposals (BIPs). As their name suggests, these are community-submitted proposals, some of which may affect how the platform operates at a fundamental level.
In order for a quantum resistance BIP to be implemented it would need to be evaluated by developers, adopted by node operators and enforced by miners, requiring widespread consensus among participants.
Depending on the significance of the upgrade, the new quantum-resistant chain could be backward compatible with previous versions of the Bitcoin blockchain, and hence would only require a soft fork to implement.
There are already proposals to switch Bitcoin over to quantum-resistant cryptography.
This includes the recent BIP-360, which seeks to introduce P2QRH (Pay-to-Quantum-Resistant-Hash) — a type of isogeny-based cryptography. This does not involve integer factorization, is resistant to Shor's algorithm and there is no efficient quantum algorithm to solve it.
Indeed, several blockchains already claim to offer various degrees of quantum resistance. These include Quantum Resistant Ledger (QRL), IOTA (IOTA) and Nervos Network (CKB) — though none have ever needed to resist a quantum attack.
>> Click here to keep tabs on your favorite quantum-resistant tokens.
Overall, your cryptocurrencies are safe against this potential threat vector for the foreseeable future.
This article contains links to third-party websites or other content for information purposes only (“Third-Party Sites”). The Third-Party Sites are not under the control of CoinMarketCap, and CoinMarketCap is not responsible for the content of any Third-Party Site, including without limitation any link contained in a Third-Party Site, or any changes or updates to a Third-Party Site. CoinMarketCap is providing these links to you only as a convenience, and the inclusion of any link does not imply endorsement, approval or recommendation by CoinMarketCap of the site or any association with its operators. This article is intended to be used and must be used for informational purposes only. It is important to do your own research and analysis before making any material decisions related to any of the products or services described. This article is not intended as, and shall not be construed as, financial advice. The views and opinions expressed in this article are the author’s [company’s] own and do not necessarily reflect those of CoinMarketCap. CoinMarketCap is not responsible for the success or authenticity of any project, we aim to act as a neutral informational resource for end-users.
